Patrick boyhan



( N0 Model P. BOYHA N.

LATITUDE INDICATOR.

No. 291,570. Patent ed Jan. 8 1884.

INVBNTGR ATTORNEY f I UNITED STATES PATENT rrrcn,

raraiox nornan, or New Your, N. v.

LATITUDE-INDICATOR.

, SPECIFICATION forming part of Letters Patent No. 291,570, dated January 8, 1884.

Application filed July 19 1883. (X model.)

To aZZ whom it 11mg} concern.-

Be it known that I, Px'rnrcn Borniin, a citizen of the United States, residing atNo. 633 Second avenue, in the city of New York, county of New York, .and State of New York, have invented a new and useful Latitude-Indicatoran instrument for determining the latitude of any place on the earths surfacegat any day of the year, by the sun at noon, or at any night of the year, at any' hour, by the north polar star in the northern hemisphere or the south polar. stanin the southern hemisphere, without calculation, that this invention has not been patented to myself or anyother person or persons with my consent or knowledge in any country, and that the same has not been in public use in the United States for more than two years prior to this application, and I' do hereby declare that the following is a specificationof my invention, refer.- ence being had to the accompanying drawings,.forming a part thereof.

The object of my invention is to furnish a means of determining the latitude of any place onthe earths surface where the personusing my instrument is, without calculation, when thejsun is visible at noon. from the place the latitude of which it is desired to obtain, or whenthe north polar l star or the south polar star is visible. I accomplish this result by means of my latitude-indicator -the instru-. ment above referred to-illustrated in the accompanying drawings, in whicht. Figure l is a front view of the instrument. Fig. 2 is a side view of the instrument. Fig. 3 is a sectional view of the axle and screwand parts of the instrument attached to the same. Upon the face of the metal dish: a is stamped or traced a semicircle, b,-from the center of the disk, with a diameter, a d, from which center is erected a perpendicular representing the equatorial line. x This line divides the semicircle into two equal parts with ninety degrees on either side, which are designated by lines representing degrees, half-degrees, quarter-degrees, and intermediates, (the diameter of the disk to be about two feet, or larger or smaller, as desired.) Between the described semicircle and the margin of the plate are three parallel arcs, drawn twenty-three degrees and'twenty-eight minutes on either side of the extended equatorial line, representing the position of the earth with the sun every day ofthe year.- The space between theupper and lower of these arcs is divided on the right'of the equatorial line into forty-five and one-half equal parts by straight lines traced from the upper to the lower arc, and to the left of the equatorial line 0 finto forty-six equal parts, to represent the number of. days in the year, each half-line representing two days.

The upper andlower arcs are divided into twelve parts, representing the twelve months of the year. .l hese twelve divisions are designated by the prolongation of the lines mark-f ing the divisionsiin the upper arc in a direction toward the circumference of the disk, and in the lower are in a direction toward the center of i the semicircle, the ends of the arcs representing the winter and summersolstice. Each of the twelve divisions are designated by the name of a month in the year and the numberof days in the month named, the division on the upper are which is intersectedfby the prolongation of the equatorial line 0 f being designated as September, next to the right, October, next to theright, November, the remaining number of straight lines to the right at the end of the upper are, together with the requisite number on the lower are, being in eluded under December, the next division to the left on the lower are being designated as January, the next to the left as February, the next to the left being designated as March, which is intersected by the equatorial line, the next to the left as April, the next as May, the next as June, including lines on the extreme left of the upper and lower arcs, the next to the right in the upper are as July, the next to the rightas August. i

At the center of the dish a passes a small axle with screw, 91,011 which turns freely an indicator, g, a washer, m, being placed on the axle between the disk and the indicator. One extremity of the indicator terminates in a pointer at or near the circumference of the cincle where the degrees are markedthe other extremity a short distance from the edge of the disk. To this latter extremity, 'througha small hole in it, is affixed, by means of ashort wire or chain, a weight, 72, as a plumb-bob,

which serves to retain the indicator always in a vertical position. 4

Upon the axle it also turns freely a thin metal bar, is, about one-half inch wide, awasher being placed between the indicator and the metal bar. The extremities of this bar terminate near the edge of the disk or a short distance beyond it. At the upper extremity of this metal bar is affixed, on the under side of it, just at the edge of the disk, a small piece of metal of the same or somewhat narrower widththan the bar, and of a thickness corre sponding to the distance between the disk and I the bar at the center of the disk or atthe axle,

this small piece of metal serving as a support or rest between the disk and the bar. At the end of the bar 7c,which extends beyond the edge of the disk, passes a screw, Z, which at a short distance passes through'the end of a second metal bar, t, of the same width and thickness as the first, which extends from the screw across the back of the disk, within a short distance of the edge of the disk, being attached to the axle at the center upon which it moves, a washer being placed between the disk and the bar.- A short distance from the, edge of the disk there is attached by means of a hinge, q, asmall metal bar, extending beyond the edge of the disk, to which isaffixed a small thin metal plate,which is held in position,when in u se,by a small spring at the edge of the plate, about one inch-and a quarter in diameter, in such a position that when the small bar is parallel with the back of the disk the plate 8 will be at right angles with the bar it that crosses the face of the instrument; upon the metal bar 7a, passing across the face of the disk, is affixed a metal tube, t, the ends of which terminate near the edge of the disk, which is used for getting the line of the sun and stars, on the end of which tube is an eye-piece with a sight-hole. On a continuation of the equatorial line e f is a small hole near the edge of the disk, on either side of which there are other small holes, these holes being large enough to permit the passage of a hook by means of which the instrument is suspended. The disk at, referred to in the above specification, should be preferably of metal. The surface of the small plates should be dark-colored, so as to show most clearly the rays of the sun passing through the tube.

The method of using the instrument in ascertaining the latitudeof a place at noon when the sun is visible is as follows: Hold, place, or suspend the instrument so that it will be in a vertical position north and south, with the face of the instrument toward the west. Move the metal bar is over the face of the disk at until a small pin, 1;, marking the center of the side of the bar k nearest the face of the disk, is directly upon the day of the month on which the instrument is being used, as indicated on the arcs a: y 2. Then turn the screw Zso that the bars are tightened to the disk. Then move the disk in aline with the sun and until the rays of the sun fall directly through the tube 2' and show upon the plate 8 a circle semicircle a, as above referred to.

termining the latitude of a place at any time of the night by the north polar star in the northern hemisphere and the south polar star in the southern hemisphere is as follows: Set the bar so that the pin will be directly on the prescribed diameter 6 cl. Then turn the screw Z so that the bars 7c and p are tightened on the disk. Then let the observer look through the tubei. Then move the instrument until the star is seen through the tube. The indicator will then point to the number of degrees marking the latitude north or south of the equator of the place where the person making the observation is.

The principle upon which my instrumentis constructed is as follows: The latitude of a place is the distance north or south of the equator. By reason of the inclination of the earths axis to the plane of its orbit, the sun has an apparent motion north of the equator twentythree degrees twenty-eight minutes and south of the equator twenty-three degrees twentyeight minutes during the course of the year, As the dates of the summer and winter solstice are known, as well as the dates of the V61" nal and autumnal equinox, the number of (16* grees which the sun is north or south of the equator may be represented on the annexed diagram by the arrangement above described by a straight line drawn from the center of the of a circle to the point in the are x or 2, representing the day of the month on which the latitude is sought to be obtained. This line makes with the center of the plane of the equator an angle, which is measured on the circumference of the semicircle a.

Now, it is apparentthat if the place the latitude of which is sought to be obtained is the same number of degrees north or south of the equator as the sun is on the day in question, the angle last referred to will measure the latitude of the place. Therefore to find the latitude of any place which is north or south, or, in other words, is nearer to or farther from the equator, at the time when it is desired to ascertain the latitude, it is evident that the angle made by the vertical line of the place with the center of the plane of the equator will be greater or less than the angle ascertained by the line drawn from the center of the This difference between the angle of latitude and the angle of the suns position as represented by the degrees can be ascertained by measuring on the meridian of the place the are between the po sition of the sun on that meridian and the point of intersection of the vertical line of the" place with that meridian. This is ascertained by means of my instrument, which, on being adjusted as specified in the above description. measures the difference of these angles by means of the indicator, which is a vertical line. V

The explanation of the working of my i11- strument in ascertaining the latitude of a place when the north or south polar star is visible from that place is as follows: The distance of the earth from these stars is so great that to a person standing at the equator andlooking at the star through the tube of myinstrument he would be on a horizontal line with it, and the indicator would point to no degrees; but as he passes from the equator north or south to look at the star through the tube (which is fixed parallel with the diameter) it is necessary for him to place it at an angle which would be greater or less in proportion to the distance that he is away from the equator. This distance is measured by the are described by the indicator as it moves from the equator north or south.

means employed by me in my instrument, as

more particularly set forth in the above speci fieation.

I therefore claim A latitude-indicator consisting of a disk, a, on which is inscribed a semicircle divided into ninety degrees on each side of an equatorial line, also above said semicircle divisions eX- tending twenty-three degrees twentyeight minutes on each side of said equatorial line, said divisions representing the place of the sun during the days of theyear, bars 7c and t, with 40 clamp-screw Z, pointer g, plumb h, tube '5, cross plate 8, said bars, pointer, and tube being suit ably pivoted to said disk a, as shown and de! 

